1. Field of Invention
This invention relates to an improved artificial diet for rearing Catolaccus grandis, an ectoparasite of the boll weevil.
2. Description of the Prior Art
In recent years, the potential of the ectoparasitoid Catolaccus grandis (Burks) as a biological control agent against the boll weevil, Anthonomus grandis Boheman, has been established by a number of investigators including Johnson et al. (1973, Environ. Entomol., 2.112-118), Morales-Ramos & King (1991, Evaluation of Catolaccus grandis (Burks) as a Biological Control Agent Against the Cotton Boll Weevil, page 724, In D. J. Herber & D. A. Richter eds.!, Proc. Beltwide Cotton Conferences 1991, Vol. 2, Proc. National Cotton Council of America, Memphis, Tenn.), Morales-Ramos & Cate (1992, Ann. Entomol. Soc. Am., 85:469-476), Summy et al. (1992, Southwest. Entomol., 17:279-288), and Morales-Ramos et al. (1994, Suppression of the Boll Weevil First Generation by Augmentative Releases of Catolaccus grandis in Aliceville, Ala., pp. 958-964, In D. J. Herber & D. A. Richter eds.!, Proc. Beltwide Cotton Conferences 1994, Vol. 2, National Cotton Council of America, Memphis, Tenn.). A number of biological attributes of C. grandis have been reported which enhance its utility as a biological control agent. These attributes include higher fecundity than that of the boll weevil (Morales-Ramos & Cate, ibid); adaptability to a variety of environments, including Mississippi (Johnson et al., ibid), Central Texas (Cate et al., 1990, Pests of Cotton, pp. 17-29, In D. H. Habeck, F. D. Bennett & J. H. Frank eds.!, Classical Biological Control in the Southern United States, South. Coop. Ser. Bull. 355), the Rio Grande Valley (Summy et al., ibid), and North Alabama (Morales-Ramos et al., 1994, ibid); high searching efficiency under low host population densities (Morales-Ramos & King, 1991, ibid); ability to search for hosts on the ground where the susceptible boll weevil stages occur (Summy et al., 1992, ibid); synchrony with the boll weevil life cycle (Morales-Ramos & Cate, 1993, Environ. Entomol., 22:226-233); and adaptability to ranges of temperatures similar to those tolerated by the boll weevil (Morales-Ramos & Cate 1992, Environ. Entomol., 21:620-627).
Augmentative releases of C. grandis have been successfully used to control boll weevil populations in experimental fields in the Rio Grande Valley as described by Summy et al. (1993, Suppression of Boll Weevil Infestations by Augmentative Releases of Catolaccus grandis, pp. 908-909, In D. J. Herber & D. A. Richter eds.!, Proc. Beltwide Cotton Conferences Vol. 2, National Cotton Council of America, Memphis, Tenn.) and in commercial cotton fields in Aliceville, Ala. as described by Morales-Ramos et al. (1994, ibid). However, because C. grandis lacks the ability to overwinter in the U.S. (Johnson et al., ibid), populations of this ectoparasitoid must be rereleased each year. The use of C. grandis as a biological control agent against the boll weevil therefore depends on the development of mass propagation technology.
The current method of mass propagation consists of encapsulating boll weevil larvae in Parafilm.RTM. (Cate, 1987, Southwest. Entomol., 12:211-215). This method of encapsulation has been modified by Morales-Ramos et al. (1992, Feasibility of Mass Rearing of Catolaccus grandis, a Parasitoid of the Boll Weevil, pp. 723-726, In D. J. Herber & D. A. Richter eds.!, Proc. Beltwide Cotton Conferences 1992, Vol. 2, National Cotton Council of America, Memphis, Tenn.) and mechanized by Roberson & Harsh (1993, Mechanized Production Processes to Encapsulate Boll Weevil Larvae (Anthonomus grandis) for Mass Production of Catolaccus grandis (Burks), pp. 922-923, In D. J. Herber & D. A. Richter eds.!, Proc. Beltwide Cotton Conferences, Vol. 2, National Cotton Council of America, Memphis, Tenn.), but, the high costs of using these methods make the price of augmentative releases of C. grandis 5-10 times higher than other methods of boll weevil control.
Despite the success of C. grandis augmentative releases in controlling boll weevil populations in experimental fields, commercial application of this technology is greatly limited by the high costs of mass propagating this parasitoid. Mass propagation has been identified as a critical constraint in commercializing augmentative releases of natural enemies (King & Morrison, 1984, Some Systems for Production of Eight Entomophagous Arthropods, pp. 206-222. In E. G. King & N. C. Leppla eds.!, Advances and Challenges in Insect Rearing, USDA-Agric. Research Serv., New Orleans, La., p. 306). Development of artificial diets for in vitro rearing of parasitoids is viewed as the scientific advance necessary for opening the path for the commercial application of biological control by augmentation of natural enemies (King, 1993, Augmentation of Parasites and Predators for Suppression of Arthropod Pests, pp. 90-100, In R. D. Lumsden & J. L. Vaughn eds.!, Pest Management: Biologically Based Technologies, Proceedings of Beltsville Symposium XVIII, USDA-ARS, Beltsville, Md., American Chemical Society, Washington, D.C.).
Artificial diets for in vitro rearing of hymenopteran ectoparasitoids have been described. Thompson (1975, Ann. Entomol. Soc. Am., 68:220-226) described an artificial diet for Exteristes roborator (Fabricius), while Guerra et al. (1993, Entomol. Exp. Appl., 68:303-307) described an artificial diet for both Bracon mellitor Say and C. grandis. Both diets were devoid of insect components and were composed of amino acid, mineral, vitamin, lipid and carbohydrate fractions. The main differences between these two diets are found in the ratios and amounts of the amino acids in the amino acid fraction. Moreover, Thompson used albumin as a supplement and Guerra et al. used fresh egg yolk.
Guerra et al. subsequently modified the artificial diet described in the 1993 publication, replacing the antimicrobial agent, and adding an antimycotic, and describing an improved technique for egg deposition (1994, Entomol. Exp. Appl., 72:11-16).
Both Thompson and Guerra et al. reported successful development of parasitoids feeding on their respective diets. However, an extensive evaluation of the biological characteristics of the in vitro- reared parasitoids was not presented; and none of the parasitoids were field released. The difficulty of producing large numbers of in vitro- reared parasitoids of sufficient quality has probably been the most important factor limiting the evaluation of their biological attributes. Production of uniformly high quality parasitoids is critical to success of the augmentative release approach. The release of poor quality parasitoids may considerably reduce the degree of success of augmentation practices.